THE MAGNETO TELEPHONE SYSTEM

Some of the early telephones worked on the Magneto system.  The telephone was wired to a central switchboard that would connect the caller to another telephone via cords.  This system could work on extremely long lines and was used well into late 20th Century in the US and Australia as they had many long lines in farming communities.  In the US a single wire would run along fence posts, across hills and connect to many farms all on the same line.    The operator knew how many times to ring each farmer, plus the farmers could call each other, by using the generator on their telephone.  The downside was you had multiple users on one line!

The telephone microphone was powered by a local battery and called the exchange switchboard by means of a hand generator.  The switchboard would also call telephones by the use of a hand generator.  On finishing a call both telephone users would go on hook and then crank their generators to signal to the exchange switchboard that they had hung up (this is known as ringing off).

The downside of the Magneto system is that each telephone requires a battery to power the transmitter.  This battery required a lot of maintenance and most Magneto exchanges were changed to the Central Battery type, where the telephones did not require local power.  But Magneto was retained for, out of the way, rural areas.

Magneto Telephones
On lines within the same building, the battery-ringing telephone is generally adopted, owing to its cheapness.  On long lines it is necessary to introduce a relay to economise battery power, and in such circumstances the magneto-ringing telephone is generally preferred. It will be seen that the transmitter, the primary of the induction coil, and the speaking battery form a local circuit.  This circuit may be closed either by a gravity switch or a microtelephone press key.  With the telephone resting, the magneto bell in series with a condenser is connected across the lines via the contacts of a switch forming part of the magneto generator and a second switch forming a portion of the gravity switch.  When the handle of the magneto generator is turned, the bell is disconnected and the generator is connected across the A and B wires.  When the receiver or microtelephone is removed from its rest, the local speaking circuit is closed, the magneto bell disconnected from the line, and the receiver in series with the secondary winding of the induction coil is connected across the A and B wires.  The method in which these circuit changes are effected in the types of telephone instrument used in a magneto system varies considerably, but the principle remains the same.

GPO Exchange Codes
These are the codes, used in the BPO List of Exchanges, to indicate the type of equipment in use.

Outgoing Calls

A subscriber calls the exchange by means of the generator provided. The call would be answered by the switchboard operator who would cross connect the caller to the requested subscriber's line.  If the called line is free the operator would call the telephone by means of a generator and when answered would leave the line allowing the two subscribers to talk to each other.  The operator then associated a ticket with the connection which had all the call information printed on it.

On the conclusion of conversation, the subscriber, after replacing the receiver, turns the generator, to indicate to the exchange that the call has terminated and the ringing current operates an indicator or relay associated with the exchange cord connecting circuit.  The operator then drops the connection and finalises the ticket with the call length.

Typical Magneto Switchboards (BPO)

Typical Magneto telephones (Not all BPO)

Last revised: October 01, 2025